We have developed during the past four years a highly sensitive fluorometric method for the quantitation of long chain lipid bases (Sphingosine and its congeners), (abbreviation: LCLB) by fluorometric scanning of TL-chromatograms of their dansyl derivatives. We are now planning to apply this method to quantitative biological studies concerning the distribution of the sphingolipids in the following materials: a.) Various structures of the central and peripheral nervous system; myelinated fibers of brain (optic nerve); peripheral nerves (sciatic nerve), nonmyelinated nerve fibers of avertebrates. We plan to study comparatively the quantitative distribution of gangliosides in functionally different areas of the gray matter of brain, spinal cord, in retina, in autonomous ganglia (superior cervical ganglion of the rabbit). In these comparative studies, the reference values for the analytical data will be the amount of phospholipid phosphorus per weight unit of the analyzed material. This will allow an approximate correction for the difference between the variable amounts of connective tissue in the analyzed samples. b) A special aim of these distribution studies would be to obtain data concerning the proportions sphingosine: dihydrosphingosine in myelin from brain (optic nerve) Spinal cord, and sciatic nerve. These investigations will be carried out with species of different classes of the animal kingdom, particularly of vertebrates. The method referred to in the first sentence is the only available ultramicromethod permitting the separate quantitation of dihydrosphingosine (sphinganine) and sphingosine (sphingenine).